<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <button>点击</button>
  <script>
    // 获取元素
    const btn = document.querySelector('button');
    btn.addEventListener('click',function () {
      alert('快快点击')
    })
    btn.addEventListener('click', function () {});
  </script>
</body>
</html>